Science
A force is a push or a pull on an object.
A force changes the motion of a moving object.
A force can be strong or weak and it always has a direction.
The earth is a planet that goes around the sun in a circular orbit.
The speed of its motion doesn't change, but the direction of its motion does.
The earth has a layer of gas above its surface, which helps to support life.
Atoms are the building blocks of matter.
At the center of an atom is its nucleus, which has a positive electric charge.
Outside the nucleus are electrons, which have a negative charge.
Asteroids and comets, are objects that obey our sun, but are smaller than planets.
Asteroids that pass closed to the Earth are called near-earth objects.
The layer of gases just above Earth's surface is our atmosphere.
The atmosphere is made up of gases, such as oxygen and nitrogen.
Without an atmosphere, there would be no life on Earth.
A force can increase or decrease the speed of an object, and it can change the direction of motion.
If they collide with Earth they could cause an extinction event.
The electric force between the nucleus and the electrons holds the atom together.
Geometry
The two lines on the left intersect each other at a right angle, which is 90 degrees.
The two lines on the right are parallel, which means they never cross.
The adjacent sides of a rectangle are perpendicular, which means they meet at a 90 degree angle.
The opposite sides of a rectangle are equal and parallel, which means they never cross.
The area of a rectangle is the length times the width.
A circle is a two dimensional figure with a radius and circumference, which is the distance around the circle.
The area of a circle is PI R squared, well, R is the radius and PI is the ratio of a circle's circumference to its diameter.
A sphere is a three dimensional figure with a radius and a volume, which is 4/3 PI R cubed.
All points on the surface of a sphere are equidistant from its center.
A right triangle is a two dimensional figure with 3 sides, two of which are perpendicular.
To find its area, multiply the length of the two perpendicular sides, A & B, and divided by two, A equals one half A B.
A rectangle is a two dimensional figure with 4 sides.
